Embodiments of the present disclosure generally relate to multicast traffic in shortest path bridging networks, and, in particular, to supporting interdomain multicast routing.
PIM (Protocol Independent Multicast) can satisfy the need for multicast forwarding inside a single domain or autonomous system, which is not the case with multicast applications intended to provide services outside the boundary of a single autonomous system. For Inter Domain multicast, other protocols such as Multicast Source Discovery Protocol (MSDP) can be used.
With PIM-SM a typical multicast framework inside a single domain is composed of one or more rendezvous points (RPs), multicast sources and multicast receivers. An RP is responsible for registering sources and linking them to receivers. MSDP is designed to make multicast sources available for other domain receivers by communicating this information between RPs in different domains.
Multicast Source Discovery Protocol (MSDP) is a PIM family multicast routing protocol defined by Experimental RFC 3618. MSDP interconnects multiple PIM Sparse-Mode (PIM-SM) domains which enables PIM-SM to have Rendezvous Point (RP) redundancy and inter-domain multicasting (examples are described in RFC 4611).
MSDP typically uses TCP as its transport protocol. Each multicast tree has to have its own RP. All of the RP's are peers (directly or through other MSDP peers). Messages contain a) Source of Data, and b) Group Address The Data Source Sends To; i.e., (S,G). When an RP on its own domain receives a message, it determines if there are group members on this domain interested in a multicast. If someone is interested it triggers a join towards the data source (into the source domain) in the way of (S, G). Typically, in a peering relationship, one MSDP peer listens for new TCP connections on the well-known port 639.
An Inter Domain IP Multicast deployment consists of multiple independently operated multicast networks (domains) being able to exchange multicast traffic from one network to another. In order to provide redundancy these multicast networks are interconnected in a redundant fashion at multiple routers and interfaces.
One of these networks could be a Shortest Path Bridging (SPB) Network. SPB is a transport network protocol that provides logical Ethernet networks on native Ethernet infrastructure using a link state protocol to advertise both topology and logical network membership. Packets are encapsulated at the edge of an SPB network either in mac-in-mac 802.1ah or tagged 802.1Q/802.1ad frames and transported only to other members of the logical network. Unicast and multicast are supported and all routing is on symmetric shortest paths. Many equal cost shortest paths are supported. An SPB Multicast solution should rely on configuring the Ingress BEBs to ensure that any given multicast stream has a single entry point in the SPB Network. Also, MSDP peering to the SPB network should be accomplished in a way that does not go beyond the scaling limits of the multicast routers in the neighboring networks.